Heretofore, the environmental testing of electronic components was routinely done at a temperature of 85.degree. C. and 85% relative humidity, resulting in little or no data after many test hours lasting over a period as much as two to three months. In response to the needs of the electronic industry requiring an accelerated temperature/humidity testing in their quality control and research and development testing of integrated circuits, as well as other materials associated with the manufacture of these components, the environmental chamber of the present invention has been devised which is capable of maintaining temperatures in the range of 80.degree. C. to 150.degree. C. and humidities in the range of 70% to 95% relative humidity. Testing of the electronic components at 150.degree. C. and 85% relative humidity provides the required test data within twelve to sixteen hours which heretofore required two to three months of testing at 85.degree. C. and 85% relative humidity.
The environmental chamber of the present invention comprises, essentially, a test chamber adapted to receive the component to be tested, the test chamber being pressurized and supplied with moisturized, heated air to obtain the desired climatic condition. The environmental chamber includes a spray conditioning chamber partitioned from the test chamber, and having a plurality of water spray jets, a mist eliminator, an electric air heater, and a circulating fan. The test chamber includes a perforated air supply plenum and return plenum which communicates with the spray conditioning chamber, whereby air from the test chamber flows through the return plenum into the spray chamber. The air leaves the spray chamber substantially saturated and passes through the mist eliminator, across the air heater, which raises the temperature of the air to the desired dry bulb temperature and then through the circulating fan into the supply plenum.
The water flow circuit for the spray chamber includes a receiving tank communicating with the spray chamber, whereby water from the spray chamber flows by gravity into the receiving tank, the water level of which being controlled by a float operated switch electrically connected to a water supply pump. A circulating pump is connected to the receiving tank and runs continuously, pumping water from the tank through an electric resistance heater positioned at the outlet of the circulating pump, the heated water being pumped to the water spray jets in the spray conditioning chamber.
To compensate for heat loss, the test chamber is surrounded by an insulated housing having a door spaced from a door on the test chamber. The construction and arrangement of the double door assembly allows for the door on the test chamber to effect a pressure seal while the door on the housing effectively isolates the test chamber from any appreciable heat loss. All through piping extends parallel to the wall of the test chamber in a space between the test chamber and the insulated housing to thereby eliminate cold spots for the accumulation of condensation on the piping; and condensation on the blower shaft is eliminated by the use of a small amount of surface heat on the blower shaft sleeve.